1. Field of the Invention
The present invention relates to sterilization systems, and more particularly, to a circuit for recirculating, filtering and controlling the vapor content of the gaseous medium in a sealable enclosure.
2. Description of the Prior Art
Conventional gaseous sterilization systems typically flow sterilant into the sterilization chamber and exhaust the sterilant to a drain. An open system is described in Picard et al. U.S. Pat. No. 4,435,194. A problem often associated with such open systems is the safe disposal of residual gases. An open flow-through sterilization system that eliminates the problem of residual vapors is described in Cummings et al., U.S. Pat. No. 4,909,999 issued Mar. 20, 1990, entitled "Flow-Through Vapor Phase Sterilization System". One means of providing a closed system is taught by Cummings et al., but that means does not address the problem of moisture build up in the system to be described below.
Several closed systems for steam sterilizers have been developed which recirculate the steam rather than exhausting it. Arrangements for steam autoclaves are disclosed in Linder U.S. Pat. Nos. 3,443,884 and 3,773,466. Another closed steam sterilization system is described in Childers U.S. Pat. No. 4,808,377. In the closed steam sterilization systems, the steam is passed from the sterilization chamber, condensed, passed to a liquid storage compartment and eventually directed to a heater for conversion to steam and reuse in the sterilization chamber.
When the sterilant is steam, moisture in the closed system is not a problem. It is simply recycled for further use in the sterilization process. If other gases were to be used as the sterilant in a closed system, e.g., ethylene oxide, vapor phase hydrogen peroxide or ozone, the buildup of moisture would be highly detrimental to the sterilization process.
When the sterilant of choice is vapor phase hydrogen peroxide, which is typically generated from an aqueous solution of liquid hydrogen peroxide, the natural tendency of hydrogen peroxide vapor to degrade to oxygen and water would exacerbate the problem of moisture buildup in a closed system. The elimination of the need to dispose of residual sterilant vapors, however, commends a closed system for vapor phase hydrogen peroxide sterilization.
An object of the present invention is to provide a closed gaseous sterilization system in which the moisture content of the gases can be controlled. A further object of the present invention is to provide such a system which can be used to sterilize a variety of existing enclosures. Finally, it is an object of the present invention to eliminate problems associated with the disposal of residual sterilant vapors.